1. Field of the Invention
This invention relates to a microcapsule composition comprising a core containing at least one water-soluble, hormonally active polypeptide and optionally a polymer hydrolysis modifying agent encapsulated in a biodegradable, biocompatible copolymer excepient. These compositions have sustained release characteristics. More specifically it relates to microcapsules wherein the core contains water-soluble polypeptides which are luteinizing hormone-releasing hormones, or mammalian growth hormones or polypeptides having thymosin-like activity and optionally an organic acid or its salts, or an acidic, neutral or basic inorganic salt which is capable of modifying the hydrolysis rate of the polymer excipient, encapsulated by a biocompatible, biodegradable excipient. These microcapsules demonstrate a sustained release of drug over time, particularly when administered parenterally.
2. Related Art
There are several publications that disclose combinations of polymers and drugs designed to give sustained or delayed release of drugs. For example U.S. Pat. No. 3,773,919 discloses controlled drug release compositions in which the core comprises a drug encapsulated in polylactide/glycolide copolymers. See also U.S. Pat. No. 4,293,539 which relates to microencapsulated antibacterial compound formulations.
Microencapsulated compositions for sustained release of enzymes, hormones, vaccines, and other biologicals are mentioned in a paper by T. Chang, J. Bioeng., Vol 1, pp 25-32, 1976.
Polylactic acid polymers, polylactide/glycolide copolymers and polyglycolic acid polymers and related materials, for surgical elements and the like, incorporating a medicament and demonstrating slow release properties have been prepared. See for example U.S. Pat. Nos. 3,991,776; 4,118,470; 4,076,798.